Process for making tetramethyl lead



lid ldfild Fatenteel Aug. 19%2 t it l .1 titt d l area ass-acre llitltll'lfid FUR MAZQLNG TETRAMETHYL LEAD .lohn M. S. ,larvie, Eastwood,New South Wales, Aus= traiia, and Mathias ll. Schiller, Pittman, and.i'ohn D. Sterling, .lr.., Wenonah, Nul assign-tors to 1. du Pont deNemours Company, Wilmington, Deb, a corporation of Betas are No Drawing.Filed Aug. 19, 1969, er. No. 50,6tl5

ltd Claims. (Cl. Edd- 437) This invention relates to a process for themanufacture of tetramethyl lead, particularly by the reaction of amethyl halide with a sodium lead alloy in the presence of a catalyst.

It is Well known that tetraalkyl lead compounds are useful asantilrnocl: agents in fuels for internal combustion engines. Up to thepresent time, tetraedtyl lead has been manufactured and usedpredominantly. However, tetramethyl lead, particularly because of itshigher volatility, can be used advantageously as an antiknoclr agent inmotor fuels, alone or in combination with tetraethyl lead and the likein varying proportions to improve the road performance of leaded fuels,as more fully described by Smyers et al. in US. Patent 2,310,376.Calingaert et al. in US. Patent 2,270,109, disclose a process forpreparing a mixture of tetra-methyl and ethyl lead compounds by reactinga mixture of methyl chloride and ethyl chloride with sodium lead alloyin the presence of an aluminum type catalyst. Such process results in amixture of five tetraalkyl lead compounds in which tetramethyl lead ispresent in a minor proportion. The process of Calingaert et al. does notconstitute an economical process for making pure or substantially puretetramethyl lead in large quantities and does not yield the combinationof tetraalkyl lead compounds in the proportions required for manypurposes disclosed by Smyers et al.

The manufacture of tetramethyl lead by the general alkyl halide-sodiumlead alloy reaction requires special conditions. Whereas the ethylchloride-sodium lead alloy system does not require catalysis and can beaccelerated by such substances as ketones, alcohols, acetals, etc. knownin the art, the methyl chloride-lead alloy system responds not at all orpoorly to the presence of such accelerators and to conditions otherwiseconducive to the formation of tetraethyllead. Methyl halides are uniquein that only certain catalysts of the aluminum type seem effective tobring about the formation of methylated lead compounds. Even so. thealuminum type catalysts present practical difliculties in commercialscale operation. For example, an induction period is generallyencountered before the methylation begins, when using the combination ofaluminum alloy and aluminum chloride described by Calingaert et al. inUS. Patent 2,270,109 for the manufacture of mixed methyl and ethyl leadsfrom mixtures of methyl and ethyl chlorides. Also, relatively hightemperatures (100 C.-ll C.) are required to achieve satisfactory yieldsof tetramethyl lead. The induction period and high reaction temperaturetogether present the hazard of sudden and uncontrollable reaction (Le.surges in temperature and pressure) once the exothermic methylationbegins. This can be particularly serious with tetramethyl lead becauseof the relative ease with which it can decompose explosively. Aluminumplus aluminum chloride catalysts are ineffective in at least one of thefollowing respects, to avoid the induction period, to initiate reactionat low temperatures, to provide satisfactory reaction control, and toproduce tetramethyl lead in good yield safely and in short time.

Other aluminum type catalysts suggested by Calingaert et al., forexample, trimethyl aluminum, dlmethyl aluminum chloride and the like,have the disadvantages for commercial use of being difi'icult andhazardous to han- -21 die because of their extreme sensitivity to airand to moisture. On the other hand, it is desirable to be able to usealuminum chloride which is commercially available and presents no unusalstorage and handling problems, provided satisfactorily high yields oftetramethyl lead can be obtained with it.

It is an object of this invention to provide a new and improved processfor the manufacture of tetramethyl lead. Another object is to providesuch a process which is particularly adapted for the large scalemanufacture of pure or substantially pure tetramethyl lead. A furtherobject is to provide a catalytic process for reacting a methyl halidewith a sodium lead alloy wherein the reaction is initiated without aninduction period and proceeds smoothly at relatively low temperatures toproduce tetramethyl lead in good yield. A still further obiect is toprovide a process for making tetramethyl lead which utilizes an aluminumhalide catalyst in combination with an additional agent which materiallyimproves the yield of tetramcthyl lead. Other objects are to advance theart. Still other objects will appear hereinafter.

The above and other objects may be accomplished in accord with thisinvention which involves the process for making tetramethyl lead whichcomprises mixing at a temperature below 50 C. a sodium lead alloy, atleast about 0.25 mole per mole of sodium of an alkylating agent whichconsists of a methyl halide in which the halogen has an atomic number inthe range of 17 to 53, from about 0.05% to about 5% by weight of thealloy of an aluminum halide in which the halogen has an atomic number inthe range of 17 to 53, and from about 0.1 to about parts per part ofaluminum halide of an organolead compound of the class consisting ofhydrocarbon leads and hydrocarbon lead halides in which the halogen hasan atomic number in the range of 17 to 53, heating the mixture to atemperature of from 50 C. to about 70 C. to initiate the methylationreaction, and then heating the mixture to a temperature of from about 70C. to about C. and maintaining it at such temperature until themethylation reaction is substantially complete while gradually addingsuch quantities of said methyl halide as may be required to provide atotal of at least one mole thereof for each mole of sodium.

It has been found that by carrying out the reaction in such manner,material advantages and improved results are obtained. By having theorganolead compound present when the reaction mixture is subjected toreaction conditions, particularly to temperatures of from 50 C. to about70 C., the reaction is initiated promptly without an induction period.In other Words, the presence of the added organolead compound provides asmooth and safe initiation of the methylation reaction promptly atrelatively low temperatures and ensures a smooth and controlledreaction. This is particularly important at the beginning when themixture is heated to start the reaction. In addition, the use of theorganolead compound to initiate the reaction also provides theunexpected benefit of increased yields of tetramethyl lead, over andabove the quantity added to initiate the reaction. This is particularlysurprising since tetrarnethyl lead is a product of the reaction betweenthe methyl halide and the sodium lead alloy, and it is not obvious whythe system does not respond to the presence of such organolead compoundformed in situ to give the high yields of tetramethyl lead which arecharacteristic of the process of this invention.

Broadly, the overall process comprises mixing the sodium lead alloy, themethyl halide, the aluminum halide catalyst, and a small proportion ofadded organolead compound at a temperature below 50 C. at which therelction does not readily take place, then heating the mixul'C withagitation to a temperature at which the reaction is initiated and, whenthe reaction has become well started, gradually raising the temperatureto one at which the reaction proceeds at a reasonable rate, completingthe reaction at the higher temperature, and then recovering thetetramethyl lead from the reaction mixture by conventional procedures.Reaction temperatures are usually in the range of from 50 C. to about130 C. and, for reasons of safety, the pressure preferably should bekept below about 500 p.s.i.g., for example, by cooling, controlling therate of heating and/or the amount of methyl halide in the reaction zone,and by venting. The reaction requires one mole of methyl halide for eachmole of sodium in the sodium lead alloy. The reaction may be initiatedwith all of the desired amount of methyl halide present or with afraction of the required amount of methyl halide present, followed bygradual addition of the rest of the desired amount as the reactionproceeds.

The alkylating agent employedwill consist of a methyl halide in whichthe halogen has an atomic number in the range of 17 to 53, i.e. methylchloride, methyl bromide, or methyl iodide, or a mixture of 2 or moremethyl halides. Preferably, the reaction will be carried out with methylchloride and monosodium lead alloy, NaPb. The total amount of methylhalide employed will be at least one mole and usually not more than 20moles thereof per mole of sodium as sodium lead alloy, and preferablyfrom about 1.1 to about moles of methyl halide per mole of sodium. Whenit is desired to gradually add the methyl halide during the reaction, itis best to have present at the initiation of the reaction from about0.25 to about 0.50 mole of methyl halide per mole of sodium, preferablyabout 0.50 mole, and to gradually add the rest of the methyl halideafter the reaction has been initiated. Larger amounts than about 1.5moles of the methyl halide can be used to dilute the reaction mass andaid in controlling the reaction temperature. Similarly, the methylhalide can be carried in an inert solvent, such as the hydrocarbons,hexane, benzene, toluene and the like, to dilute the reaction mass.

The process requires, as a catalyst, an aluminum halide in which thehalogen has an atomic number in the range of 17 to 53. The term aluminumhalide is used in its strict sense to mean the compounds which consistof aluminum and halogen, i.e. AlCl AlBr and A11 The aluminum halide canbe used as such or as a suspension, slurry, or solution in an inertliquid carrier such as hexane, benzene, toluene, kerosene or liquefiedmethyl halide. Metallic aluminum and aluminum alloys may be used incombination with the aluminum halide catalyst as more particularlydescribed by Calingaert et al. in US. Patent 2,270,109, but areunnecessary and usually are without significant advantage. The amount ofthe aluminum halide catalyst employed usually will be from about 0.05%to about 5% by weight of the sodium lead alloy, and preferably fromabout 0.5% to about 1.5%.

The organolead compounds employed for initiating the reaction in theprocess of the present invention will be of the class consisting ofhydrocarbon leads and hydro carbon lead halides in which the halogen hasan atomic number in the range of 17 to 53. By hydrocarbon leads is meantcompounds consisting of lead and hydrocarbon radicals, that is, in whichlead is directly joined to hydrocarbon radicals solely. Likewise,hydrocarbon lead halides means compounds consisting of lead, hydrocarbonradicals and one or more of chlorine, bro mine and iodine, in which theleadis directly bonded to 1-3 hydrocarbon radicals and 3-1 halogenatoms. The hydrocarbon radicals include alkyl, alkenyl and aryl radicalswhich usually will contain 1-10 carbon atoms. Preferably, thehydrocarbon radicals will be alkyl radicals of 1-3 carbon atoms, i.e.methyl, ethyl and propyl, and most preferably methyl radicals. Also, thealkyl leads constitute a preferred class, represented by tetramethyllead, tetraethyl lead, tetrapropyl lead, methyltriethyl lead,

dimethyldiethyl lead, trimethylethyl lead, and hexaethyl dilead, withtetrarnethyl lead being most preferred. Other representative organoleadcompounds within this invention are tetraallyl lead, phenyl triethyllead, vinyltrimethyl lead, dimethyl lead dichloride, diethyl leaddichoride, triethy lead iodide, trimethyl lead bromide, and the like.

Mixtures of any two of more of such organolead com-- pounds may be used,if desired. The organolead compound can be used as such or added to thereaction mixture as a solution in an inert solvent, for example, as asolution of from about 20% to about by weight thereof in a solvent, suchas hexane, benzene, toluene, kerosene, and liquefied methyl halide.

Usually and preferably from about 0.4 part to about 20 parts by weightof the organolead compound per part of aluminum halide catalyst will beused. Smaller amounts, down to about 0.1 part, of organolead compoundper part of aluminum halide are beneficial. Amounts larger than about 20parts of organolead compound, e.g. parts or more thereof per part ofaluminum halide, while operable, are genrally unnecessary.

It is essential for the purposes of this invention and to obtain theadvantageous results thereof that the organolead compound be present inthe reactor with the aluminum halide catalyst and the other componentswhen the mixture is subjected to reaction conditions. Accordingly,

at least part of the methyl halide and the other components are mixed ata temperature below 50 C., usually at room temperature or below, i.e.about 20 C. to about 30C. and below, and then the mixture heated to thetemperature required for initiation of the reaction. The methylationreaction can be initiated smoothly at temperatures of 50 C. to about 60C., with temperatures not higher than about 70 C. generally needed. Thereaction can be completed at such temperatures. However, the reaction isundesirably slow at such temperatures, and it is usually desirable toemploy higher temperatures of from about 70 C. to about 130 C. forcompletion of the reaction. The production of tetrarnethyl lead proceedsat reasonable rates at temperatures from about 70 C. to about 80 C.However, it is preferred to employ temperatures of from about 100 C. toabout C. for rapid completion of the reaction safely.

The importance of these results is that a greater degree of safety isachieved and at a lower operating cost, considering the hazards andexpense of using pressurized equipment and having a relatively unstableproduct such as tetramethyl lead confined at elevated temperatures. Tobe able to control temperatures and pressures is particularly importantin the early stages of the reaction where the danger of a runawayreaction is greatest. Once at least 0.5 mole of methyl halide hasreacted with the sodium lead alloy, the danger is greatly lessened andthe temperatures can be more ra idly increased to the highertemperatures where the reaction takes place at the optimum rate. Ingeneral, the rate of heating and the pressure rise resulting therefromare coordinated to prevent sharp increases therein, the temperaturebeing raised gradually to the desired maximum temperature. This gradualrise in temperature, if not too rapid, may b continuous from thetemperature of mixing the ingredients through the reaction initiationstage to the temperature desired for rapid completion of the reaction,or may be intermittent, a desired.

The reaction is effected under agitation. It is usually desirable tocarry out the reaction in the presence of an inert solid, such asgraphite or silica, as an internal lubricant, mixing aid, oranti-agglomerant for lead, since ordinarily the reaction mass tends tobe somewhat difficult to stir, probably due to the inherent tendency ofthe particles of free lead to stick together. From about 1% to about 20%by Weight of the alloy are used, depending on the dimensions of thereactor, the effective ness of the agitation means, and the proportionsof the reactants.

In practice, the methyl halide is simply added to a reactor which willalso contain the sodium lead alloy, aluminum halide, organolcadcompound, and usually an internal lubricant, such as graphite, at aboutroom temperature. In a typical run, an autoclave is loaded at roomtemperature to contain 35 pounds (about 1.5 moles per mole of sodium) ofmethyl chloride, 0.6 pound of AlCl 0.3 pound of tetramethyl lead, and 3pounds of graphite per 100 pounds of NaPb alloy, added in any order.Reaction is effected under agitation and pressure by heating to atemperature at which the methylation begins and can be maintained safelyat a practical rate. The rate of heating and the pressure rise (as aresult of heating) are coordinated to prevent sharp increases. Reactionmass temperature is controlled, by cooling the autoclave when necessary,to keep the internal pressure from exceeding about 300 p.s.i.g. Usually,a temperature of about 50 C.60 C. has to be reached to initiate thernethylation, and, once the exothermic reaction has started, thetemperature is allowed to rise (or is raised) to 100 C.l C. and heldthere until the reaction is complete.

Alternatively, the methyl chloride can be fed gradually into theautoclave containing the other components. preferably, about 0.25 toabout 0.50 mole of methyl chloride per mole of sodium is added beforethe charge is brought to 50 C.-60 C. where reaction begins. The rest ofthe methyl chloride is then fed in slowly and the temperature allowed toincrease to 100 C.1l0 C. where the reaction is completed. The pressureis kept under about 300 p.s.i.g. by cooling, controlling the methylchloride feed, and venting of non-condensibles.

To recover the product, the charge is cooled to about C.- C. andresidual methyl halide vented to a recovery system, as in tetraethyllead technology. The tetramethyl lead component can be recovered bysolvent extraction, e.g. with toluene, or by steam distillation,according to the well-known methods.

in order to more fully illustrate this invention, preferred modes ofcarrying it into effect, and the advantageous results to be obtainedthereby, the following examples are given in which the amounts andproportions are by weight, except where otherwise specificallyindicated.

Example 1 A steel bomb is charged under nitrogen to contain 2.5

parts of graphite, 0.62 part of aluminum chloride, 100 1 warming to roomtemperature, the bomb is heated over a period of 15 minutes to 110 C.,held there for 1 hour, then cooled and opened. Tetramethyl lead isobtained in 86.7% yield on extraction of the reaction mass with.isooetane.

Substantially identical results are obtained in the above procedure bysteam distilling rather than extracting the reaction Steam distillationis effected conveniently for reasons of safety in the presence of ahydrocarbon such as toluene, benze e or xylene, and the productrecove"ed as a solution, e.g. 80% by weight in the hydrocarbon.

The yield of tetramethyl lead is only 52% when aluminum chloride is usedalone in the above procedure.

On using 12 parts of tetraethyl lead in place of the tetramethyl lead asthe co-catalyst (or catalyst promoter) in the above procedure,tetramethyl lead is obtained in 61% yield.

When boron fluoride is used instead of aluminum chloride in the aboveprocedure of Example 1, no tetramethyl lead is obtained. This is incontrast to the disclosure of Calingaert et al. in US. Patent 2,270,109that this substance catalyzes the reaction of mixtures of a methylhalide and ethyl chloride with sodium lead alloy to pro duce a mixtureof methyl and ethyl lead tetraalkyl compounds.

Example 2 A stainless-steel lined pressure reactor is loaded in orderwith 3.4 parts of graphite, 1.3 parts of AlCl 100.4 parts of NaPb alloy,2.6 parts of tetramethyl lead and parts or" methyl chloride, theweight/volume ratio of the methyl chloride to the total capacity of thebomb corresponding to 0.21 gram/cc. The reaction mass, under agitation,is heated in 7 minutes to 70 C., held there for 3 hours, and cooled. Theyield of tetramethyl lead, isolated in the usual manner, is 73.8%.

In contrast, with AlCl alone (i.e. when the added tetramethyl lead isomitted), the yield of tetramethyl lead is 57.2%.

Inferior results are obtained with a mixture of aluminum chloride andaluminum alloy turnings (eg. as an alloy of percent composition 6.2-8.0Cu, 1.4 Fe, 1.3 Si, 0.5 Mn, 0.07 Mg, 2.2 Zn, 0.3 Ni, 0.2 Ti, 0.5 other,the rest Al) as the sole catalyst combination (i.e. without organolead)under the above conditions. Induction periods of up to about 1 hour areobserved before the reaction starts at 70 C., and the yields oftetramethyl lead tend to be even lower than obtained with aluminumchloride alone. For example, the yield is 45.3% when 0.34 part ofaluminum chloride and 0.21 part of the aluminum alloy are used and noorganolead is added.

Example 3 The procedure of Example 2 is repeated except that (a) thequantity of added tetramethyl lead is 1.2 parts and (b) the reactionmixture is heated in 13 minutes to 70 C., held 3 hours at 70 C., then in9 minutes raised to 110 C. and held 21 minutes at this temperature,before cooling to room temperature and discharging the product.Tetramethyl lead is obtained from the reaction mass in 80% yield.

Good yields of tctramethyl lead are also obtained by the above procedureon using parts of monosodium lead alloy, 33 parts of methyl chloride,0.6 part of tetramethyl lead and 0.6 part of aluminum chloride.

Example 4 An alkylation autoclave (equipped with agitation, temperatureand pressure control means, and inlet and outlet means) is charged atroom temperature with 15,000 parts crushed NaPb alloy, 454 partsgraphite, 98 parts alu minum chloride, 87 parts tetramethyl lead as an80% solution in toluene, and 6350 parts liquid methyl chloride, thelatter being added under pressure to the autoclave which is otherwisesealed. The autoclave is closed and the contents, under agitation, isheated during /2 hour to 65 C. to initiate the reaction, and thetemperature is controlled so that the pressure is in the range 200 to300 p.s.i.g. The temperature is gradually raised from 65 C. to C. over aperiod of 5.5 hours, the temperature rise being coordinated with thepressure which is maintained below 300 and above 200 p.s.i.g. Theautoclave is then cooled, vented to recover unreacted methyl chloride,and then discharged. From the discharged product, tetramethyl lead wasobtained in about 80% yield.

When the above procedure is modified so that 1725 parts of methylchloride is charged initially along with the other reactants, and theremaining 4625 parts are added gradually as needed to maintain 200-300p.s.i.g. pressure at a temperature within the range 65 C.1l0 C.,essentially the same yield of tetramethyl lead is realized.

Example 5 Example 1 is repeated, except that 77 parts of methyl bromideis used in place of the methyl chloride and the reaction mixture held at85 C. for 4 hours, to obtain tctramethyl lead in 71% yield.

Example 6 A S-gallon autoclave was charged under nitrogen atmospherewith 15,100 g. comminuted NaPb alloy, 490 g. flaked graphite, 30 g.aluminum alloy, 50 g. aluminum chloride, 266 g. tctramethyl lead as atoluene solution totaling 2400 g., and 2,950 g. methyl Chloride(liquefied). The autoclave was closed and the charge heated underagitation over a 45 min. period from room temperature to a reaction masstemperature of 80 C. and a pressure of about 260 p.s.i.g. Additionalmethyl chloride (2,500 g.) was then fed in slowly over a period of about1 hour, during which time the temperature of the reaction mass increasedto 88 C., and the pressure increased to 310 p.s.i.g. The reaction masswas then cooked for about 2% hours with the temperature increasinggradually to 110 C. The pressure reached a maximum of 340 p.s.i.g.before decreasing steadily. The reactor was then cooled to about 40 C.,vented, and discharged by dropping its contents to a steam still. Thereactor was rinsed with toluene and the rinsings added to the steamstill. Steam distillation of the total reaction product gave 3605 g.tctramethyl lead (corrected for the initial 266 g. and toluene). Thisyield corresponds to 82% of theoretical. In contrast, in substantiallyotherwise identical runs, one before and one after in the same reactorwherein toluene was added without tctramethyl lead, the yield1 oftetramethyl lead was 65% before and 74% afterwar s.

The aluminum alloy used in these runs was a commercial alloy of thecomposition in percent: Cu 6.0-8.0, Fe 1.4, Si l.03.0, Mn 0.1, Mg 0.07,Zn 2.2, Ni 0.3, Ti 0.2, other elements 0.5, the remainder Al.

It will be understood that the preceding examples have been given forillustrative purposes solely and that this invention is not restrictedto the specific embodiments described therein. n the other hand, it willbe readily apparent to those skilled in the art that, subject to thelimitations set forth in the general description, many variations can bemade in the materials, proportions, conditions and techniques employed,without departing from the spirit and scope of this invention.

From the" preceding description and examples, it will be apparent thatthis invention provides a new and improved process for makingtctramethyl lead in high yields which process overcomes the diificultiesand hazards involved in the prior processes. iarticularly, thisinvention eliminates the induction period ordinarily encountered inprior processes and the hazards involved therein, and permits theinitiation of the reaction at lower temperatures in a smooth and safemanner and the reaction to be readily controlled. It producestctramethyl lead as the predominant product and makes it possible tosafely and economically produce pure or substantially pure tctramethyllead in high yields. Furthermore, this invention provides a processwhereby tctramethyl lead can be readily obtained in materially higheryields than could be obtained heretofore. Accordingly, it will beapparent that this invention constitutes a valuable advance in andcontribution to the art.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. The process for making tctramethyl lead which comprises mixing at atemperature below 50 C. a sodium lead alloy, at least about 0.25 moleper mole of sodium of an alkylating agent which consists of a methylhalide in which the halogen has an atomic number in the range of 17 to53, from about 0.05% to about 5% by weight, based on said alloy, of analuminum halide in which the halogen has an atomic number in the rangeof'l7 to 53, and from about 0.1 to about 100 parts per part of aluminumhalide of an onganolead compound of the class consisting of hydrocarbonleads and hydrocarbon lead halides in which the halogen has an atomicnumber in the range from 50 C. to about 70 C. to initiate themethylationreaction, and then heating the mixture to a temperature offrom about 70 C. to about 130 C. and maintaining it at such temperatureuntil the methylation reaction is substantially complete while graduallyadding such quantities of said methyl halide as may be required toprovide a total of at least one mole thereof for each mole of sodium.

2. The process for making tctramethyl lead which comprises mixing at atemperature below 50 C. a sodium lead alloy, from about 0.25 mole toabout 20 moles per mole of sodium of an alkylating agent which consistsof a methyl halide in which the halogen has an atomic number in therange of 17 to 53, from about 0.05% to about 5% by weight, based on saidalloy, of an aluminum halide in which the halogen has an atomic numberin the range of 17 to 53, and from about 0.4 to about 20 parts per partof aluminum halide or" a hydrocarbon lead in which the hydrocarbongroups are alkyl radicals of 1 to 10 carbon atoms, heating the mixtureto a temperature of from 50 C. to about 70 C. to initiate themethylation reaction, and then heating the mixture to a temperature offrom about 70 C. to about 130 C. and maintaining it at such temperatureuntil the methylation reaction is substantially complete while graduallyadding such quantities of said methyl halide as may be required toprovide a total of at least one mole thereof for each mole of sodium.

3. The process for making tctramethyl lead which comprises mixing at atemperature below 50 C. a sodium lead alloy, from about 0.25 mole toabout 20 moles per mole of sodium of an alkylating agent which consistsof a methyl halide in which the halogen has an atomic number in therange of 17 to 53, from about 0.05 to about 5% by weight, based on saidalloy of an aluminum halide in which the halogen has an atomic number inthe range of 17 to 53, and from about 0.4 to about 20 parts per part ofaluminum halide of a tetraalkyllead in which each alkyl group contains1-3 carbon atoms, heating the mixture to a temperature of from 50 C. toabout 70 C. to initiate the methylation reaction, and then heating themixture to a temperature of from about 70 C. to about C. and maintainingit at such temperature until the methylation reaction is substantiallycomplete while gradually adding such quantities or" said methyl halideas may be required to provide a total of at least one rnole thereof foreach mole of sodium.

4. The process for making tctramethyl lead which comprises mixing at atemperature below 50 C. a sodium lead alloy, from about 0.25 mole toabout 5 moles per mole of sodium of an alkylating agent which consistsof methyl chloride, from about 0.5% to about 1.5% by weight based onsaid alloy, of aluminum chloride, and from about 0.4 to about 20 partsof tctramethyl lead per part of aluminum chloride, heating the mixtureto a temperature of from 50 C. to about 70 C. to initiate themethylation reaction, and then heating the mixture to a temperature offrom about 70 C. to about 110 C. and maintaining it at such temperatureuntil the methylation reaction is substantially complete while graduallyadding such quantities of methyl chloride as may be required to providea total of at least one mole thereof for each mole of sodium.

5. The process for making tctramethyl lead which comprises mixing at atemperature below 50 C. a sodium lead alloy, from 1 mole to about 20moles per mole of sodium of an alkylating agent which consists of amethyl halide in which the halogen has an atomic number in the range of17 to 53, from about 0.05% to about 5% by weight based on said alloy, ofan aluminum halide in which the halogen has an atomic number in therange of 17 to 53, and from about 0.4 to about 20 parts per part aoaaeroof aluminum halide of a hydrocarbon lead in which the hydrocarbon groupsare alkyl radicals of 1 to 3 carbon atoms, heating the mixture LO atemperature of from 5 C. to about 70 C. to initiate the methylationreaction, and then heating the mixture to a temperature of from about 70C. to about 130 C. and maintaining it at such temperature until themethylation reaction is substantially complete.

6. The process for making tetramethyl lead which comprises mixing at atemperature below 50 C. a sodium lead alloy, from 1 to about moles permole of sodium of an alkylating agent which consists of methyl chloride,from about 0.05% to about 5% by weight, based on said alloy, of aluminumchloride, and from about 0.4 to about 20 parts of tetramethyl lead perpart of aluminum chloride, heating the mixture to a temperature of from5 0 C. to about 70 C. to initiate the methylation reaction, and thenheating the mixture to a temperature of from about 70 C. to about 110 C.and maintaining it at such temperature until the methylation reaction issubstantially complete.

7. The process for making tetramethyl lead which comprises mixing at atemperature below 50 C. a sodium lead alloy, from about 0.25 mole toabout 20 moles per mole of sodium and an alkylating agent which consistsof a methyl halide in which the halogen has an atomic number in therange of 17 to 53, from about 0.05% to about 5% by Weight, based on saidalloy, of an aluminum halide in which the halogen has an atomic numberin the range of 17 to 53, and from about 0.4 to about 20 parts per partof aluminum halide of a hydrocarbon lead halide in which the halogen hasan atomic number in the range of 17 to 53 and the hydrocarbon groups arealltyl radicals of 1 to carbon atoms, heating the mixture to atemperature of from 50 C. to about 70 C. to initiate the methylationreaction, and then heating the mixture to a temperature of from about 70C. to about 130 C. and maintaining it at such temperature until themethylation reaction is substantially complete while gradually addingsuch quantities of said methyl halide as may be required to provide atotal of at least one mole thereof for each mole of sodium.

8. The process for making tetramethyl lead which comprises miXing at atemperature below 50 C. a sodium lead alloy, from about 0.25 mole toabout 5 moles per mole of sodium of an alkylating agent which consistsof a methyl halide in which the halogen has an atomic number in therange of 17 to 53, from about 0.5% to about 1.5% by weight, based onsaid alloy of an aluminum halide in which the halogen has an atomicnumber in the range of 17 to 53, and from about 0.4 to about 20 partsper part of aluminum halide of a dialkyl lead dihalide in which eachalkyl group contains l-3 carbon atoms and the halogen has an atomicnumber in the range of 17 to 53, heating the mixture to a temperature offrom 50 C. to about 70 C. to initiate the methylation reaction, and thenheating the mixture to a temperature of from about 70 C. to about 110 C.and maintaining it at such temperature until the metiylation reaction issubstantially complete while gradually adding such quantities of saidmethyl halide as may be required to provide a total of at least one molethereof for each mole of sodium.

9. The process for making tetramethyl lead which comprises m' ing at atemperature below 50 C. a sodium lead alloy, from about 0.25 mole toabout 5 moles per mole of sodium of an alkylating agent which consistsof methyl chloride, from about 0.5% to about 1.5% by Weight, based onsaid alloy, of aluminum chloride, and from about 0.4 to about 20 partsof dimethyl lead dichloride per part of aluminum chloride, heating themixture to a temperature of from 50 C. to about 70 C. to initiate themethylation reaction, and then heating the mixture to a temperature offrom about 70 C. to about 110 C. and maintaining it at such temperatureuntil the '10 methylation reaction is substantially complete whilegradually adding such quantities of methyl chloride as may be requiredto provide a total of at least one mole thereof for each mole of sodium.

10. The process for making tetramethyl lead which comprises mixing at atemperature below 50 C. a sodium lead alloy, from 1 to about 5 moles permole of sodium of an alkylating agent which consists of a methyl halidein which the halogen has an atomic number in the range of 17 to 53, fromabout 0.05% to about 5% by Weight based on said alloy, of an aluminumhalide in which the halogen has an atomic number in the range of 17 to53, and from about 0.4 to about 20 parts per part of aluminum halide ofa hydrocarbon lead halide in which the halogen has an atomic number inthe range of 17 to 53 and the hydrocarbon groups are alkyl radicals of 1to 3 carbon atoms, heating the mixture to a temperature of from 50 C. toabout 70 C. to initiate methylation reaction, and then heating themixture to a temperature of from about 70 C. to about 130 C. andmaintaining it at such temperature until the methylation reaction issubstantially complete.

11. The process for making tetramcthyl lead which comprises mixing at atemperature below 5 0 C. a sodium lead alloy, from 1 to about 5 molesper mole of sodium of an alkylating agent which consists of methylchloride, from about 0.5% to about 1.5 by weight, based on said alloy,of aluminum chloride, and from about 0.4 to about 7 20 parts of dimethyllead dichloride per part of aluminum chloride, heating the mixture to atemperature of from 50 C. to about 70 C. to initiate the methylationreaction, and then heating the mixture to a temperature of from about 70C. to about C. and maintaining it at such temperature until themethylation reaction is substantially complete.

12. The process for making tetramethyl lead which comprises initiatingat a temperature of from about 50 C. to about 70 C. the reaction of asodium lead alloy and an alkylatinag agent which consists of a methylhalide in which the halogen has an atomic number in the range of 17 to53 in the presence of from about 0.05% to about 5% by weight, based onsaid alloy, of on aluminum halide in which the halogen has an atomicnumber in the range of 17 to 53 and from about 0.1 to about 100 partsper part of aluminum halide of an organolead compound of the classconsisting of hydrocarbon leads and hydrocarbon lead halides in whichthe halogen has an atomic number in the range of 17 to 53, and thehydrocarbon groups contain 1 to 10 carbon atoms and are selected fromalkyl, allcenyl and aryl radicals, then heating the mixture to atemperature of from about 70 C. to about C. and maintaining the mixtureat the latter temperature until the methylation reaction issubstantially complete.

13. The process for making tetramethyl lead which comprises initiatingat a temperature of from about 50 C. to about 70 C. the reaction of asodiurn lead alloy and an alkylating agent which consists of a methylhalide in which the halogen has an atomic number in the range of 17 to53 in the presence of from about 0.05% to about 5% by Weight, based onsaid alloy, of an aluminum halide in which the halogen has an atomicnumber in the range of 17 to 53 and from about 0.4 to about 20 parts perpart of aluminum halide of a hydrocarbon lead in which the hydrocarbongroups are alkyl radicals of 1 to 10 carbon atoms, then heating themixture to a temperature of from about 70 C. to about 130 C. andmaintaining the mixture at the latter temperature until the methylationreaction is substantially complete.

14. The process for making tetramethyl lead which comprises initiatingat a temperature of from about 5 0 C. to about 70 C. the reaction of asodium lead alloy and an alkylating agent which consists of methylchloride in the presence of from about 0.05% to about 5% by spa-acre ll. Weight, based on said alloy, of aluminum chloride and from about 0.4to about 20 parts of tetramethyl lead per part of aluminum chloride,then heating the mixture to a temperature of from about 70 C. to about110 C. and maintaining the mixture at the latter temperature until themethylation reaction is substantially complete.

15. The process for making tetramethyl lead which comprises initiatingat a temperature of from about 50 C. to about 70 C. the reaction of asodium lead alloy and an alkylating agent Which consists of a methylhalide in which the halogen has an atomic number in the range of 17 to53 in the presence of from about 0.05% to about by Weight, based on saidalloy, of an aluminum halide in which the halogen has an atomic numberin the range of 17 to 53 and from about 0.4 to about 20 parts per partof aluminum halide of a hydrocarbon lead halide in which the halogen hasan atomic number in the range of 17 to 53 and the hydrocarbon groups arealkyl radicals of 1 to 10 carbon atoms, then heating the mixture to atemperature of from about 70 C. to about 130 C. and I maintaining themixture at the latter temperature until the methylation reaction issubstantially complete.

16. The process for making tetramethyl lead which comprises initiatingat a temperature of from about C. to about C. the reaction of a sodiumlead alloy and an alkylating agent which consists of methyl chloride inthe presence of from about 0.5% to about 1.5% by Weight, based on saidalloy, of aluminum chloride and from about 0.4 to about 20 parts ofdimethyl lead dichloride per part of aluminum chloride, then heating themixture to a temperature of from about 70 C. to about C. and maintainingthe mixture at the latter temperature until the methylation reaction issubstantially complete.

References Cited in the tile of this patent UNITED STATES FATENTS2,270,109 Calingaert et al. Jan. 13, 1942

1. THE PROCESS FOR MAKING TETRAMETHYL LEAD WHICH COMPRISES MIXING AT ATEMPERATURE BELOW 50*C. A SODIUM LEAD ALLOY, AT LEAST ABOUT 0.25 MOLEPER MOLE OF SODIUM OF AN ALKYLATING AGENT WHICH CONSISTS OF A METHYLHALIDE IN WHICH THE HALOGEN HAS AN ATOMIC NUMBER IN THE RANGE OF 17 TO53, FRAOM ABOUT 0.05% TO ABOUT 5% BY WEIGHT, BASED ON SAID ALLOY, OF ANALUMINUM HALIDE IN WHICH THE HALOGEN HAS AN ATOMIC NUMBER IN THE RANGEOF 17 TO 53, AND FROM ABOUT 0.1 TO ABOUT 100 PARTS PER PART OF ALUMINUMHALIDE OF AN ORGANOLEAD COMPOUND OF THE CLASS CONSISTING OF HYDROCARBONLEADS AND HYDROCARBON LEAD HALIDES IN WHICH THE HALOGEN HAS AN ATOMICNUMBER IN THE RANGE OF 17 TO 53 AND THE HYDROCARBON GROUPS CONTAIN 1 TO10 CARABON ATOMS AND ARE SELECTED FROM ALKYL, ALKENYL AND ARYL RADICALS,HEATING THE MIXTURE TO A TEMPERATURE OF FROM 50*C. TO ABOUT 70*C. TOINITIATE THE METHYLATION REACTION, AND TAHEN HEATING THE MIXTURE TO ATEMPERATURE OF FROM ABOUT 70*C. TO ABOUT 130*C. AND MAINTAINING IT ATSUCH TEMPERATURE UNTIL THE METHYLATION REACTION IS SUBSTANTIALLY COMPLETWHILE GRADUALLY ADDING SUCH QUANTITIES OF SAID MWTHYL HALIDE AS MAY BEREQUIRED TO PROVIDE A TOTAL OF AT LEAST ONE MOLE THEREOF FOR EACH MOLEOF SODIUM.